October 2006 - Boost-users - lists.preview.boost.org

bug in boost::multi_index::sequenced splice (patch)
by Hubert Schmid 02 Oct '06

02 Oct '06

Hi, I guess there is a bug in boost/multi_index/sequenced_index.hpp. The following program fails to compile, because there is no matching operator== for class C. But this operator shouldn't be required for splice. #include "boost/multi_index/sequenced_index.hpp" #include "boost/multi_index_container.hpp" struct C { }; int main() { using namespace boost; using namespace boost::multi_index; typedef multi_index_container<C, indexed_by<sequenced<> > > Cs; Cs cs; cs.push_back(C()); cs.splice(cs.end(), cs, cs.begin()); // XXX: compile error } The following program compiles, but both assertions fail at runtime: #include "boost/multi_index/sequenced_index.hpp" #include "boost/multi_index_container.hpp" int main() { using namespace boost; using namespace boost::multi_index; typedef multi_index_container<int, indexed_by<sequenced<> > > ints; ints foo; foo.push_back(42); ints bar; bar.push_back(42); foo.splice(foo.end(), bar, bar.begin()); assert(foo.size() == 2); assert(bar.size() == 0); } I have made both tests with the boost library in Debian/unstable (version 1.33.1-7). I have also compared the source file sequenced_index.hpp with the CVS-MAIN version (1.12). I guess the following patch should fix this bug: --- sequenced_index.hpp.orig 2006-09-29 11:38:06.000000000 +0200 +++ sequenced_index.hpp 2006-09-29 11:39:43.000000000 +0200 @@ -355,7 +355,7 @@ BOOST_MULTI_INDEX_CHECK_DEREFERENCEABLE_ITERATOR(i); BOOST_MULTI_INDEX_CHECK_IS_OWNER(i,x); BOOST_MULTI_INDEX_SEQ_INDEX_CHECK_INVARIANT; - if(x==*this){ + if(&x==this){ if(position!=i)relink(position.get_node(),i.get_node()); } else{ @@ -388,7 +388,7 @@ BOOST_MULTI_INDEX_CHECK_IS_OWNER(last,x); BOOST_MULTI_INDEX_CHECK_VALID_RANGE(first,last); BOOST_MULTI_INDEX_SEQ_INDEX_CHECK_INVARIANT; - if(x==*this){ + if(&x==this){ BOOST_MULTI_INDEX_CHECK_OUTSIDE_RANGE(position,first,last); if(position!=last)relink( position.get_node(),first.get_node(),last.get_node()); regards, Hubert

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Re: [Boost-users] Whitespace ins boost::filesystem::path
by shookie＠email.de 02 Oct '06

02 Oct '06

Ok, found the name_checking constructors, and now slap me for all that it's worth. I apologize for my 4:00 in the morning 15 h straight coding session mishaps. I should have slept before before crying out loud ;) Regards Jan Schukat

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Re: [Boost-users] [function] How do you bind two boost::functionobjects together?
by Sohail Somani 02 Oct '06

02 Oct '06

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org > [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Jason House > > I want the result of the bound expression to have one input parameter > that would be decided later. For instance: > > bool some_function(char x); > boost::function<bool (char) some_function_object(some_function); > boost::function<bool (int)> f = convert(some_function_object) > std::cout << f(32); I think what you're looking for is composition of functions? i.e. g o f (x) => g(f(x))? The right nomenclature might help... What it seems you want to do is to generate a function that does this: bool the_result(int i) { return some_function(convert_to_char(int)); } Is that right? I know you can curry with boost function + lambda but I haven't tried composition myself (though it should be possible!)

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How to pass data to thread
by Monica Gretzer 02 Oct '06

02 Oct '06

Hi, I want to pass data to a thread function. My question is- what is wrong with this code? The compiler error output is: "error: function returning a function". In the code below I am trying to pass an int to the thread function. // ------------- code: how to pass data to the thread ? ---------------- #include <boost/thread/thread.hpp> #include <boost/bind.hpp> #include <iostream> using namespace std; class TestThread { public: void thread(int a); void CreateThreads(void); }; void TestThread::thread(int a) { cout << "I am thread " << a << endl; } void TestThread::CreateThreads() { boost::thread t1( boost::bind( &TestThread::thread, 10)); boost::thread t2( boost::bind( &TestThread::thread, 20)); // wait for the thread to finish t1.join(); t2.join(); } int main() { TestThread t; t.CreateThreads(); }

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bind/function: composition
by Johan Torp 02 Oct '06

02 Oct '06

I often tend to have interfaces which take a boost::function<void()> that is to be called when an event occurs. Quite often I need make two separate function calls as response to one event. In these cases I usually solve the problem using the following technique: void foo(); void bar(); void call_two(const boost::function<void ()>& one, const boost::function<void ()>& two) { one(); two(); } boost::function<void ()> on_event = boost::bind(&call_two, boost::bind(&foo), boost::bind(&bar)); Is there any other way to acheive this, beside having to redeclare and define a function such as call_two? It seems quite easy to define something like: template <typename R1, typename R2> void nullary_compose boost::function<R1 ()>& one, const boost::function<R2 ()>& two); template <typename R1, typename R2, typename R3> void nullary_compose boost::function<R1 ()>& one, const boost::function<R2 ()>& two, const boost::function<R3 ()>& three); ... Is anybody else interested in seeing such templates in boost? Best Regards, Johan Torp -- System Developer TouchTable AB Tel: +46 (0)31 773 68 12 johan.torp(a)touchtable.se

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Inverse matrix
by Karin Thomas 02 Oct '06

02 Oct '06

I would like to know whether Boost library is convenient for calculating an inverse matrix. Or does anyone suggest another way to do it? Kind regards, Karin Thomas

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[date_time] Stricter stream input validation
by Johan Nilsson 02 Oct '06

02 Oct '06

Hi, is there any way to force ptime stream input fail when the time duration part is not between 00:00:00 and 23:59:59? I'm using a time_input_facet with a formatting string of "%Y-%m-%d %H:%M:%S" imbued into a streams with exceptions(failbit) enabled. I'd like an exception raised when time parts such as 25:00:00 are parsed instead of getting the next day's date. I guess I could use regex validation, but was hoping to have support for this in the date_time library. Currently using cvs boost (RC_1_34_0). Thanks / Johan

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[date-time]time zone input
by Sean Huang 02 Oct '06

02 Oct '06

Jeff, Do you plan to add the time zone input support to date-time anytime soon. Specifically, I am asking for using "%q" and "%Q" on input. Thanks, Sean

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Array of smart pointers to base class
by scott velasquez 02 Oct '06

02 Oct '06

Here is what I desire to have in my GUI library as it pertains to boost: 1. No raw widgt pointers. Container functions should take a reference to a base class smart pointer type rather then accepting raw pointers of the base class type. 2. Containers store an array of smart pointers of the base GUI widget type. This is needed because containers can contain many widget derived types. I'm just showing the class code that matters; Normally, you would have constructors, destructors, access label, etc. class OWidget; class ODerivedWidget : public OWidget; class OWidgetContainer : public OWidget { public: void Add( boost::shared_ptr<OWidget>& widget ) { mWidgets.pushback(widget); } std::vector<boost::shared_ptr<OWidget>> mWidgets; } int main(void) { OWidgetContainer root; // Works just fine since the types match boost::shared_ptr<OWidget> base(new OWidget()); root.Add(base); // Doesn't work since the Add() function can't convert ODerivedWidget shared pointer to OWidget shared pointer type. boost::shared_ptr<ODerivedWidget> derived(new ODerivedWidget()); root.Add( derived); } Is this even possible? I've read about boost::any and boost:variant and while that might solve my problem of storing smart pointers of differing types, it doesn't allow me to pass smart pointers of derived types. Any ideas/suggestions would be GREATLY appreciated! -scottv

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Re: [Boost-users] [boost] [spirit] 1.8.4 release candidate + roadmap
by Hartmut Kaiser 01 Oct '06

01 Oct '06

Arkadiy Vertleyb wrote: > Just a few questions to clear some confusion: > > 1) Is Spirit 1.8.4 the same Spirit that is currently in Boost CVS? Yes, at least in the RC_1_34_0 branch. > 2) Which version of Boost does Spirit 1.8.4 use? Any resonable (>= 1.31). The miniboost contained in the Spirit 1.8.4 release is based on Boost 1.33.1 (but we will re-release Spirit after V1.34 has been released). > 3) Which version of Spirit will be a part of Boost 1.34? 1.8.4, to avoid confusion we probably will bump the version, though. HTH Regards Hartmut > > Regards, > Arkadiy > > > > _______________________________________________ > Unsubscribe & other changes: > http://lists.boost.org/mailman/listinfo.cgi/boost

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